Color photography



Aug 17, 1943- G. P. GRANT, .1R

v coLoR PHOTOGRAPHY Filed Deo. 1l, 1939 BY /mm aL/Mm ATTO RN EYS is-important, however, that there be base I of paper, Celluloid or glass coated with a I4 of a transparent material for a gelatinous photosensitive emulsion and for the stripping layer I3, such as collodion, or gelatin admixed with a solvent such as acetone, may advantageously be applied over the coating I3, and on top of the layer I4 is disposed a single sensitized emulsion I5, of the panchromatic positive reversal type. By positive reversal I mean that the emulsion is such that the image as projected thereon may be developed, bleached oif and washed, the remainder exposed to light and re-developed, or otherwise treated in order to change the negative to a positive. A suitable panchromatic, positive reversal emulsion may comprise a precipitate of specially sensitized silver halide particles distributed throughout a coagulated gelatinous film, applied as a smooth an'd uniform layer. It may be made by treating the photo sensitive chemicals in a known positive-reversal type of emulsion such as that known by and sold under the trade name Direx` bythe Positype Corporation of America, with organic compounds which render the emulsion panchromatic.

It should be understood that one or more of the above mentioned layers may be omitted or the said layers may be rearranged in various ways without departing from the invention. It present on the raw paper stock or other support Ill a smooth surface or layer to which the emulsion I5 will adhere and from which it may be stripped at the conclusion of the process. For instance, the stripping and binding layers above described may be omitted and the waterproofing layer used orv arranged so that it may be used to serve the purpose thereof. A waterproof layer is of advantage in order to minimize the absorption by the support of the chemicals of the photographic emulsion and treating fluids and to reduce the likelihood of relative movement between the photographic emulsion and the support caused by expansion and contraction.

Generally described, the process of the present invention proceeds by making three color separation exposures on separate pieces of sensitized material of the nature described. -The images created by exposures of the emulsion to light through the optical system of a camera, are developed, and instead of being xed, washed and dried as in the prior art, they are reversed from negatives topositives, treated to impart a desired color thereto, and then each is pressed in face to face relationship against the surface of a previously prepared backing and adhered thereto.

The backing may be constructed as illustrated in Figure 2 and may comprise a sheet 20 having 4a gelatinous coating 2i on its surface, to which the first colored positive, indicated at I51, ad-

heres. The colored positive having been adhered to the backing, the base or support IEB is stripped therefrom.

astralesv y The other positives, toned with suitable colors. are then applied in registry with the first and their bases or supports I0 successively stripped olf until all three of the colored positives are applied to the backing.

A feature of the invention is 'that negative lms are each created on their original bases or supports, reversed, toned and otherwise treated in situ upon such support, and-only after they have been completed in the form of separate vcolored positives and properly registered on a backing are they stripped from their supports. This obviates the difficulty of handling the thin emulsion films constituting the prints, except as they are secured to and upon their supports I0, and insures their complete and accurate registry.

Another feature of the invention is that it is not necessary to fix, wash and dry the negative,

as in the ordinary color processes, nor is it necessary to make a separate exposure through the negative onto special strippable paper or otherwise, in order to obtain separate positive images.

Coming now to a more detailed description of the process, I may proceed as follows:

1. I first make three color separation exposures by exposing three panchromatic, positive reversal sheets such as are shown in Figure l, to focused images from a suitable lens system. This may be accomplished in a one shot camera by placing a color filter in front of each photosensitive sheet; for instance, I may use a green filter in front of one sheet in order to filter out red and blue light, a blue filter in front of an'- other to lter out the yellow and red light, and a red filter in front of the third to filter out the blue-green light.

2. After each sheet is so exposed the impressed image is developed by a suitable developer and rinsed. This removes the salts from the areas Where the light has effected a chemical change in the emulsion, and produces a negative.

3. The sheet is immersed in a bleaching solu- -tion such as potassium dichromate or permanganate, and sulphuric acid in order to remove the developed image of the negative.

4. It is again immersed in a clearing solution such as sodium sulphite or bisulphite to remove the yellow residue left by the bleaching.

5. 'I'he negative is then flashed;" that is, it is exposed to a white light in order to activate the areas which were originally unaffected by the light image.

6. The flashed" photosensitive layer is then redeveloped; that ls, the areas affected by the flash are developed and rinsed. At this point the reversal is complete and the sheets'carry positives instead of negatives. They have black and White positive images, each representing the densities of one of the three basic colors, red, yellow and blue.

7. Each positive is toned; that is, a color is imparted according to the nature of the particular image, Whether it received the red, yellow or blue rays. One way of toning is as follows:

(a) Immersing in a bleaching solution such as potassium ferrocyanide and hyposulphite, in order to convert the metallic silver to silver ferrocyanide.

(b) Immersing each positive into a special solution in order to replace the silver in the silver ferrocyanide with some metal which produces a salt of the desired color, either red, yellow or blue. Thus each positive is colored with one of the basic colors.

s. A backing paper 2o (see Figure 2), ls soaked in water to soften the gelatinous coating 2 l therepositives is brought backingv 2@ and adhered thereto.

9. If one or more ofthe intermediate layers Il, i2, i3 or i4 have notI been sumciently softened or is similarly registered and stripped so that the nal yresult is three of the colored films in registered relationship on the backing 2t?. This produces the finished colored print in which the original colors are ire-created.

The original sheet l@ has been retained throughout the process and not discarded until after the top photosensitive nlm has changed tives. The entire process may be carried out with a minimum expenditure of time and materials.

It is pointed out that although it is advantageous to retain the emulsion in association with the base or support itl up to the time the emul- A transparent strengthening nlm of collodion, which may comprise the binding layer M, may be provided adjacent the emulsion in order to facilitate this operation.

One way of toning the positive by converting the silver particles constituting the image in the emulsion into a colored salt, is as follows:

For obtaining a red image of the positive, the following solutions are prepared:

Solutions A and E are freshly mixed, combined and then acidied withy a few drops of dilute nitric acid, andv the sheet or print is immersed therein until bleached. It is then Washed and placed in' solution minutes, whereupon it is removed For obtaining a ing' the following C for several and washed.

blue tone a solution comprisis prepared and the redeveloped print immersed therein:

Ferrie ammonia citrate...v gramsn 2 Potassium ferricyanide do 2 Tartaric acid --do 7 Water c. c-- 50o Since this toner gives considerable intensification of' the image. the print should be under printed but fully developed.

For yellow the following solutions may be prepared:

Solution A:

Acetic acid (glacial) c. c 5 Lead nitrate s grams- 3 Potassium erricyanide do 2 Water c. c-- 200 Solution B:

Potassium dichromate --gram l Water c. c-- 20G The print is bleached in solution A, washed and then placed in Solution B for several minutes.

lt should be noted that `it is not necessary to nx the print since the toning procedure aiiects all parts of the image produced by the flashing and redeveloping operations. The reversal has already eliminated the parts that the plain hyposulphite solution comprising ing hath is intended to remove,

Another way in which thev positive image may be colored or toned is as follows:

After the sheet is ashed it is immersed in a special redeveioping solution comprising, for blue, l0 parts of Solution A, made up of:

Solution A:

Sodium sulphite grams 18 Sodium carbonate do 40 Potassium bromide do l 2 amino-5 diethylamino toluene nionohydrochloride -do l.

Water to maizel liter.- 1 and one part of a 1% solution of 2,4-dichloro-1- naphthol in ethyl alcohol.

For yellow the special redeveloper may consist of 10 parts A, and l part of a 1% solution dichloroanilide in ethy] alcohol.

For red, lil parts of Solution A may be used with l part of a 1% solution of p-nitrophenylacetonitrile in ethyl alcohol.

In each of the three foregoing treatments the redeveloper changes the silver halide to metalof acetoacet-2,5

f in a solution known as "Farmers reducer,

which does not affect the dye images.

Still another Way in which the immersing the sheet, after the clearing operation of hereinbefore numbered 4, in suitable polysulphides in order to convert the silver halide of the positive to salts of the desired color.

It is to be understood that the specific constructions, operations and compositions above described are illustrative merely and do not limit the invention. Such changes and modifications as are apparent to those skilled and in the art may be made without departing from the invention as herein shown, described and claimed.

Having thus fully described the invention, what is claimed as new and desired to be secured by Letters Patent is:

l. The process of making colored prints comprising forming a plurality of color separation exposures on a panchromatic, positive reversal strippable emulsion secured to a support, developing said exposures and converting them into positives, coloring said positives, adhering one of said positives to a backing, stripping the support therefrom, and thereafter adhering another positive to the first in registered relationship therewith and stripping its support therefrom.

2. The process of making colored photographic -prints comprising forming a plurality of color separation exposures on a panchromatic, positive reversal emulsion secured to a support, developing said exposures, reversing the same and therby forming positives, coloring said positives, adhering one of said positives to a backing, stripping the support therefrom, adhering another positive to said backing in super imposed and registered relationship with the first and then stripping its support therefrom.

3. The process of making colored photographic prints comprising forming a plurality of color separation exposures on a panchromatic, positive reversal emulsion secured to a support, developing said exposures. reversing the same and thereby forming positives, coloring said positives, coloring each itives, adhering one of said positives to a backing, stripping the support therefrom, adhering another positive to said backing in superimposed relationship with the rst, stripping its support therefrom, adhering a third positive to said backing in superimposed and registered relationship with the rst two positives and then stripping its support therefrom.

4. The steps in the process of making colored photographic prints which steps comprise supporting a panchromatic, positive reversal emulsion on a sheet, disposing separate sheets in a camera., separately activating the emulsion'on each sheet with the light rays comprising one of the primary colors, and thereby forming three color separation exposures, developing and reversing each exposure and thereby forming pospositive and then transferring the same in superimposed relationship to a backing, retaining the emulsion on the first mentioned sheet until the transfer to the back is completed. i

5. The steps in the process of making colored photographic prints which steps comprise supporting a panchromatic, positive reversal emulsion on a' sheet, disposing separate sheets in a camera, separately activating the emulsion on Y each sheet with the light rays comprising one of the primary colors, and therebyiorming three colorseparation exposures, developing and reversing each exposure and thereby forming positives, coloring each positive, adhering one colored positive to a backing and stripping said sheet from such positive and thereafter registering and adhering a second positive in superimposed relationship to the first and stripping the supporting sheet therefrom.

GARNET PETER GRANT, yJR. 

